1. Field of the Invention
The instant invention concerns servo steering systems for motor vehicles.
2. Background of the Prior Art
This general type of servo steering system is known in German Patent 1,025,281; here, the valve member is constructed as a single-piece control piston having a section which communicates with the groove, having an annular groove within said section; the lever communicates with the annular groove. Since the groove, as well as the annular groove, communicate with one of the operational spaces, the full operational pressure is able to develop therein. For this reason, it was necessary in the prior art to construct the control piston in a single piece in the described manner, whereby a pressure-equalization takes place at the communicating point of the lever, namely, in the annular groove, which thereby prevents the development of pressure-forces in the axial direction. The arrangement of two control pistons, which has already been successfully utilized in other cases, wherein said control pistons are activated, for example, only after a lost motion, or via spring-elastic transmission means, was impossible in prior art, since the pressure in the operational spaces places a stress on the front side of the control pistons which would thereby be pushed apart in an undesired manner, and this would render such an arrangement as non-functional.